PbTiO3ferroelectric thin film gate fet for infrared detection

Abstract

A field effect transistor with a PbTiO₃ ferroelectric thin film gate has been prepared as an infrared sensor which works at room temperature and has an infrared sensitivity in a wide spectral range. PbTiO₃ thin film was deposited with rf sputtering at substrate temperatures of 300–550°C. A dielectric constant of 200 and a maximum remanent polarization of 27 μC/cm² were obtained in the films deposited on platinum foil. Pyroelectric response of the film on platinum-coated mica was obtained with a voltage responsivity R_v and detectivity D* of 330 V/W and 1.5 × 10⁸ cm√Hz/W with a bandwidth of 1 Hz respectively at 20 Hz by using infrared light coming through a Ge filter from an incandescent lamp. This film was deposited on the gate of a Si MOSFET to control the surface potential on the current channel. This FET has also pyroelectric sensitivity with R_v and D* of 390 V/W and 3.5 × 10⁵ cm √Hz/W with a bandwidth of 1 Hz respectively at 20 Hz. Fast response with a rise time of ∼3.5 μsec is obtained by measuring the output under CO₂ laser pulse irradiation.